How can I get rid of Japanese beetles?
The Japanese beetle is a very destructive landscape pest. The adult attacks the flowers and foliage of hundreds of plant species while the larvae eat grass roots. The best long-term control of future populations is to target the grubs, which overwinter in the soil and emerge as adults in spring.
Milky spore (a bacterium), applied to the lawn, causes a lethal disease specific to the Japanese beetle grubs. It does take a few years to become effective however. For adults, hand pick the beetle and discard in a pail of soapy water. Use a neem oil spray to attack them. Keep in mind that many birds such as cardinals, catbirds and grackles are the natural enemies and favor the grubs or beetles, or both. So try to attract birds to your garden.
Courtesy of the NYBG Plant Information Service